Color negative origination silver halide photographic films are a class of photosensitive materials that map the luminance (neutral) and chrominance (color) information of a scene to complementary tonal and hue polarities in the negative film. Upon exposure and development of the film to form dye images from photographic couplers incorporated in the film, light areas of the scene are recorded as dark areas on the color negative film, and dark areas of the scene are recorded as light areas on the color negative film. Colored areas of the scene are typically recorded as complementary colors in the color negative film: red is recorded as cyan, green is recorded as magenta, blue is recorded as yellow, etc. In order to render an accurate reproduction of a scene, a subsequent process is necessary to reverse the luminance and chrominance information back to those of the original scene. In the motion picture industry, one such subsequent process is to optically print (by contact or optics) the color negative film onto another negative working photosensitive silver halide material which produces dye images upon exposure and development, such as a motion picture silver halide print film, to produce a color positive image suitable for projection.
Historically, color print silver halide photographic materials, such as EASTMAN EXR Color Print Film 5386.TM., have been optimized to yield pleasing projected prints when used in conjunction with color negative origination silver halide photographic materials as discussed above. That is, the sensitometric properties of print materials are co-optimized by considering the properties of the printing device to be used and the nature of a representative color negative tonescale to be printed, such as that of KODAK VISION 500T Color Negative Film 5279.TM.. When a motion picture color negative is printed on motion picture color print stock, the sensitometric properties of the two materials combine to yield an acceptable scene reproduction in the print film when projected on a theater screen. To facilitate obtaining optimal reproductions, guidelines exist regarding the exposure of the camera original negative (for example see American Cinematographer Manual, Dr. Rod Ryan Ed., 7.sup.th Edition, The ASC Press, Hollywood, Calif., 1993, pp128-141.), exposure of the print stock (LAD-Laboratory Aim Density KODAK Publication No. H-61), and projector/screen luminance levels (Society of Motion Picture and Television Engineers (SMPTE) Standard 196M-1995).
In order to obtain a high quality visual image in an optical photographic print, the contrasts for each color record of the negative film and print film designed for producing optical prints are conventionally maintained within certain ranges (e.g., mid-scale contrasts of about 0.45-0.7 for negative films and about 2.5-3.1 for print films), as too low a contrast may result in production of flat-looking positive print images with black tones rendered as smokey-grey and white tones rendered as light gray, while too high a contrast may result in poor flesh tone reproductions and loss of shadow detail. Pictures such as these would not be pleasing to view and would be deemed to be of low quality in the industry.
Correct exposure of camera negative originals has long been emphasized not only to ensure that critical scene information is properly recorded but also so that when the negative is printed on a photographic print film according to trade practice, scene blacks are sufficiently dense in the resulting projected prints. The importance of obtaining substantial black densities is such that cinematographers often over-expose camera negatives as a means of obtaining good blacks. Dense camera originals require higher light levels to be used in the printing step. When the printing light is increased, the exposure delivered to the photographic print film from the Dmin area of the camera film is higher, resulting in greater dye generation upon photographic processing and resulting higher black densities. This effect is well know in the trade (American Cinematographer Manual, p281). Even with overexposure techniques, however, maximum equivalent neutral (i.e., visual) densities obtainable for conventional silver halide photographic print films are generally limited to about 3.8, where the equivalent neutral density of any particular dye color record is defined as the visual density that results when the other two dyes are added in quantities just sufficient to produce a neutral gray (see, e.g., "Procedures for Equivalent-Neutral-Density (END) Calibration of Color Densitometers Using a Digital Computer", by Albert J. Sant, in the Photographic Science and Engineering, Vol. 14, Number 5, September-October 1970, pg. 356). Over-exposures additionally can result in loss of highlight detail in a resulting print. Additional special image processing techniques are also known in the art for raising black density levels in conventional photographic silver halide print materials, such as by-passing the bleach step present in normal print processing so as to retain developed silver (see, e.g., B. Bergery, "Reflections: The Lab, Part II", American Cinematographer, May 1993, pp. 74-78). The retained silver increases print opacity yielding higher black densities, but with an accompanying loss of color saturation. Additionally, given the need for large throughput in the creation of theatrical release prints, nonstandard processing is burdensome and impractical.
Alternatives to silver halide photographic print films are known which provide desirably high print black density levels. Dye imbibition transfer prints, e.g., are able to achieve much higher dynamic ranges than commercially available color-coupled silver halide photographic films. Visual densities as high as 5.0 are possible, while the current color-coupled print films are limited to densities of about 3.8. The imbibition printing process, however, is disadvantageous as it requires the formation of three separation matrix films and complex registration procedures during the transfer of dyes to a receiving blank to form a print film.
Given the desire to have high black densities in projected prints, it would be advantageous to raise the overall contrast of color-coupled silver halide photographic print materials in order to raise the Dmax of such films, by either changing film silver laydown and/or coupler levels or through modification of film processing conditions. Unfortunately, in doing so, the contrast of flesh reproduction would also be typically undesirably raised and image shadow detail may be lost (shadows may be blocked in) upon conventional printing as discussed above. Thus there is an apparent conflict in establishing an optimal contrast level for photographic print stock: to obtain high black densities, the contrast should be at a maximum, but high contrast levels prove to be detrimental to flesh and shadow-detail reproduction. There is a simultaneous need for good blacks and sufficient shadow density. Therefore, for conventional printing, a high contrast print stock would generally not be acceptable.
Processes for inserting a digital image data manipulation step in conventional photographic image generation processes prior to making a final picture print are known in the art. Digital image data, obtained directly or by scanning optical (analog) images with a digital film scanner, can be extensively manipulated, using computer processing and look-up table mapping, before recording back out onto film (see, e.g., U.S. Pat. No. 5,574,659, and J. E. Boyd, J. Appl. Photo. Eng., Vol 8, 1982, pp15-22). In the motion picture industry, such digital image data may conveniently be recorded on a motion picture intermediate negative film, such as EASTMAN Color Intermediate Films 2244, 5244, and 7244, with a digital film recorder such as a CINEON LIGHTING Digital Film Recorder. As discussed in Boyd, special film-reproduction curves can be created to simulate any desired gamma, relative film speed, and/or toe/shoulder responses, and such curves may be implemented using custom look-up tables in film recorders. The reproduction response of digitally exposed film can be completely variable, unlike conventionally exposed film which has a sensitometric response that can be altered only slightly with changes in development time and temperature. The characteristic curve of the film and exposure of the camera film determine the overall density of the final image, with limited changes in contrast and film speed possible during development.
Digital film recorders (e.g. CINEON LIGHTNING Digital Film Recorder), particularly those using lasers as their exposing sources, are capable of creating digital modified negatives (e.g., on EASTMAN Color Intermediate Films 2244, 5244, and 7244) with a dynamic range of 2.0 printing density. In the motion picture industry, however, color photographic silver halide print films which are used in conjunction with digitally created or modified output material are typically the same as those that have been optimized for the direct or release optical printing of color photographic silver halide negative films. Such motion picture silver halide photographic print stocks are accordingly designed with latitudes commensurate for use with typical color negative photographic film dynamic ranges, typically 1.5 printing density or less. The design constraints imposed by the latter use make these print materials sub-optimal for use with digitally output material. As a result, the inherent dynamic range available from film/digital recorder combinations is not fully realizable in projected prints. The upper-scale contrast of conventional photographic silver halide print stock is such that lighter densities on the recorded negative map to a region of decreasing contrast in the print stock, preventing the achievement of high print densities that are desirable for scene blacks. As a result, there is a distinct limitation to the black density that may be achieved, in spite of the insertion of advantageous digital processing steps prior to printing.
It would accordingly be desirable to provide a color-coupled silver halide photographic print film element which would enable higher black densities and improved color saturation when used with digitally created or modified negatives or when exposed directly in laser film recording devices in order to permit the full flexibility and dynamic range inherent in digital processing to be realized in projected photographic prints. It would be further desirable to provide such an element which is robust and easily manufactured, and which may be used in current printers and processors without requiring any modifications to standard exposure and development processes.